Aircraft Maintenance: Aircraft cockpit lighting
Panel lighting, Part 1
If you fly at night, it’s fairly important to be able to see the aircraft instruments. It’s also important to be able to see and identify all the switches and circuit breakers in the cockpit. The goal of panel lighting in an aircraft is to make the instruments and controls easy to read, while preserving the pilot’s night vision. Unfortunately, most general aviation aircraft have poor panel lighting at best, which leads to the requisite 14 flashlights that every pilot seems to carry distributed among a flight bag, aircraft pockets, kneeboard, shirt pocket, and forehead. It doesn’t have to be that way.
There are four major types of aircraft panel lighting: instrument face lighting, post lighting, flood lighting, and back/edge lighting.
Post lighting is a flexible means of adding nonintrusive lighting in a variety of different situations. Small lights are housed within raised “posts” that have hoods at the top, directing the lighting down across the panel. They are effective for about three to four inches in most cases and cover an area limited by the hood itself. The hood can usually be rotated to better direct the light onto the item to be illuminated. Post lights are designed with a screw base that is the same size as instrument mounting screws, so they conveniently do double duty in both lighting and securing the instrument. Although post lights are not the most attractive form of panel lighting, their flexibility allows them to be used to provide lighting for switches and other controls as well. On our Bonanza, the fuel selector is located down by the pilot’s left leg. Two post lights illuminate the selector control and placard nicely.
Flood lighting is the next common form of panel lighting. As the name implies, the strategy here is to provide a light source to flood an entire area with light. This is commonly done through lights in the aircraft glare shield that are directed down across the panel. While flood lighting is an effective form of illuminating the entire panel, it is also the most detrimental form of lighting to the pilot’s night vision. Judicious use of the dimmer is required to balance the ability to read the instruments and controls on the panel, yet not flood the entire cockpit with light to the point of sacrificing the ability to see outside the aircraft. Lighting colors play an important role here as well, with many aircraft employing red flood lighting to reduce night vision loss.
The last form of panel lighting is the most eloquent, but it is also the most expensive. Panel backlighting and edge lighting is accomplished by projecting a light through a translucent engraved or painted panel from behind, from the edge, or from within the panel. Panels lit internally are called electroluminescent panels. Text and labels appear to glow, making it easy for the pilot to read switch identifications, placards, etc. Edges around openings in the panel are similarly effective, with light allowed to bleed out from unpainted edges of the cover plates, illuminating controls and switches.
Regardless of which methods of panel lighting are installed in the aircraft you fly, the combination should allow you to easily identify and interpret all controls, switches, circuit breakers, and placards. Night flying is a challenging task, and it’s important that you be able to focus your attention outside the aircraft without worrying about seeing what you need to inside the aircraft as well. Next time, we will cover strategies for repairing and improving the panel lighting in your aircraft. Until then, happy flying!
